Do communication protocols exist as a hierarchy, or are they all considered separate from each other?

This may be an odd question, but I'm trying to familiarize myself with as many communication protocols as I can and I'm trying to make it easier for myself.
As an example of what I mean by my question: could I2S be considered a subset of SPI protocol? Both share a clock line and data line between a master and slave device, and whereas SPI is defined for general synchronous communication, I2S is specifically designed for audio.10.0.0.0.1192.168.1.254hotmail.com